1. Field of the Invention
The present invention relates to a fixation arrangement on the outer surface of an electrode head mounted at a distal end of a pacing lead.
2. Description of the Prior Art
A pacing lead may be a multipolar (or unipolar or bipolar) electrode lead used for providing intracardial stimulation of heart tissue, and/or for sensing heart signals, by means of a pulse generator or some other type of heart stimulation apparatus. The pacing lead carries the stimulus from the pulse generator to the cardiac tissue, or relays intrinsic cardiac signals back to a sense amplifier of such a pulse generator. The fixation arrangement on the outer surface of the electrode head normally includes an attachment mechanism with one or more tines (and/or fins) adapted to lodge in the trabeculae lining the inner wall of the heart without actually penetrating the cardiac wall.
A tined electrode head (i.e. an electrode head provided with tines) is useful for providing reliable anchoring of the electrode head and its lead in the trabeculae (trabecular network) inside the heart. The barb or fluke-like tines become entangled in the trabecular network thereby securing the electrode head position.
Although tines are very effective for anchoring the electrode head, implantation and repositioning procedures may be facilitated if the tines are foldable and extendable as for instance disclosed in U.S. Pat. No. 4,957,118. This document illustrates a mechanical way of extending and folding the tines by means of a threaded stylet.